Reid Machine maximized early voting turnout. The one "swing" state that was probably baked before Election Day. When one side turns out a ridiculous percentage of their voters and they have two weeks of in-person early voting (on top of an even longer period for mail absentees, I believe), the other side is at a severe disandvantage. This year was probably an Election Day blowout for Trump, but he still lost by several points in terms of the total NV vote.
This wasn't specific to this year, it's been a trend in the state for much of Reid's tenure. Since he's retiring in January, one would guess that some of that advantage would dissipitate. Overall it's a state that seems tailor-made for Trump (one of the highest percentages of WWC voters of any state), so it might be a reasonable target in 2020.
Is CCM inheriting the Reid machine? You would think Sandoval would be popular enough to put together a counter-coalition.